Liquid hydrocarbon distillate fuels containing hydrocarbon-soluble betaines as antistatic agents



United States Patent ()filice 3,027,246 Patented Mar. 27, 1962 3,027,246LIQUID HYDROCARBON DISTILLATE FUELS CQNTAllNlNG HYDROCARBON S DLUBLEBETATNE AS ANTESTATEC AGENTS Philip Lee Bartlett, Wilmington, Del.,assignor to E. I. du Pont de Nernours and Company, Wilmington, Del, acorporation of Delaware No Drawing. Filed Nov. 3, 1958, Ser. No. 771,2159 Claims. (Cl. 44-66) This invention is directed to the treatment ofhydrocarbons, such as the distillate fuels, which tend to accumulatepotentially hazardous electrostatic charges in service. Acording to thepresent invention, the addition of a hydrocarbon-soluble betaine to astatic-prone hydrocarbon substrate minimizes the accumulation of staticelectricity in such substrate.

The accumulation of electrical charges in the handling of hydrocarbonsis widely recognized as a serious hazard. A number of explosions andfires that have occurred in recent years during the bulk handling ofdistillate fuels and solvents have been attributed to the accumulation(and subsequent discharge) of static electricity in the systemsinvolve-d. Some handling conditions that contribute to the rapidgeneration of dangerous charge levels are rapid flow of fuel throughpipelines and hoses, splash filling of receiving vessels (storage tanksand seagoing tankers), and, mixing of the fuel with water.

The problem of static formation in the distillate fuels is ofconsiderable concern to the military as well as to the petroleumindustry, and much searching has been and is being done to find asolution thereto. The results of a number of investigations indicatethat most distillate fuels would be expected to produce substantialamounts of static electricity under service conditions, and practicallyall produce sufiicient static electricity to ignite vapor-air mixtures,providing there is present a mechanism for collecting and dischargingthe electricity. The production of static electricity in such fuels isassociated with the presence of colloidal impurities which are ionic orwhich are capable of becoming ionized in the hydrocarbon environment.These impurities are believed to be either naturally occurring orrepresent fuel degradation and oxidation products or residues fromtreating operations. As a result of preferential adsorption ofpositively or negatively charged ions from the impurities on thecontainer (e.g. wall or hose lining), the fuel will acquire a charge ofthe opposite sign. The rate of production of static electricity inliquid hydrocarbons increases with the flow rate and is accelerated bythe presence of small amounts of water, air and dispersed solids. Sinceleakage of the charge from the body of the hydrocarbon is normally avery slow process, a potential may soon be established during the normalhandling of the fuel to ignite fuel-air mixtures or to cause submergedexplosions within the fuel when the electricity finally discharges. Theproblem is particularly acute with jet fuels.

As discussed in Electrostatics in the Petroleum Industry, edits/.1 by A.Klingenberg and J. L. van der Nenne, Elsevier, 1958, expedients such asgrounding the apparatus, blanketing of the fuel with inert gases, andmechanical modifications in the handling procedures are helpful but notentirely satisfactory safeguards. The most promising approach appears tobe the use of additives. To be practical, particularly for use in jetfuels where stringent specifications have to be met, an antistaticadditive should (1) be effective, in technically feasible smallconcentrations, in fuels of both charge types i.e. in positive prone andnegative prone fuels; (2) have no adverse effect on water-tolerancecharacteristics of the fuel (3) have no adverse effect on jet fuelthermal stability; (4) have no adverse effect on fuel storage stability;

and, (5) be non-metallic since metals in general adversely affect fuelstability and contribute to the formation of combustion deposits, and,tend to embrittle alloys used for turbine engines.

Deficient in at least one of the above requirements are the polarcompounds suggested heretofore; compounds such as metal or ammonium(including quaternary ammonium) salts of inorganic and organic acids(including acids of phosphorus, sulfur and carboxylic acids) arerepresentative of such polar compounds. For example, Rogers, McDermottand Munday, Static Electricity in Petroleum Products, Oil and Gas J. 55,166-95 (1957), disclose that all the additives studied so far are polarcompounds which are surface active and promote the formation ofemulsions when the blends are mixed with water. Thus, they fail to meetthe water tolerance specifications of jet fuels and in adition arerather easily extracted on contact of the fuel with water.

it is an object of the present invention to provide novel antistaticagents which are significantly effective, in liquid hydrocarbons, inminimizing the accumulation of static electricity in both types ofcharge-prone liquid hydrocarbons. It is a further object of thisinvention to provide novel liquid hydrocarbon compositions containingantistatic agents which antistatic agents do not adversely af fect otherfuel properties such as water tolerance characteristics. It is stillanother object of the present invention to provide novel liquidhydrocarbon compositions containing antistatic agents, said liquidhydrocarbon being a jet fuel and said antistatic agent, in addition tominimizing the accumulation of static electricity, minimizing theadverse effects of thermal stress on jet fuels, which adverse effectsare normally encountered.

These and other objects will be apparent in the fol- I lowingspecification and claims.

More specifically, the objects of the present invention are achieved byemploying a hydrocarbon-soluble betaine, as hereinafter described andclaimed, as the antistatic agent in small quantity sufiicient tominimize the tendency of the hydrocarbon to accumulate electrostaticcharge. Such quantity will usually be in the range of from about 0.1 to30 lbs. per 1000 barrels (0.000033 to 0.01% by weight) of thestatic-prone liquid hydrocarbon. It is preferred to use an antistaticquantity of at least 0.5 lb. and not more than 15 lbs. per 1000 barrels.

Betaines which may be used according to this invention arehydrocarbon-soluble members of the class of dipolar ions represented byFormula I which follows:

where R, is a divalent hydrocarbon radical, such as an alkylene oralkylidene radical, R and R are aliphatic hydrocarbyl radicals, such asthe loWer-alkyl radicals, and R is an uncharged aliphatic radical suchas hydrocarbyl and hydrocarbyl substituted by ether (-O), hydroxyl (OH)and carbonyl (C=O) groups. R, is primarily a solubilizing group andshould be free of substituents that promote the emulsification of thefuel with water. To have sufiicient hydrocarbon-solubility the betaineshould contain at least about 11 carbon atoms and preferably at leastabout 16 carbon atoms in the molecule. Ordinarily the betaine willcontain no more than about 35 carbon atoms, and usually up to about 30carbon atoms.

Preferably, R will be an alkylene radical, particularly methylene, or analkylidene radical having up to 17 carbon atoms, such as ethylidene,propylidene, undecylidene, tridecylidene and heptadecylidene.

R and R may be the same or different C -C alkyl radicals, e.g. methyl,ethyl propyl, butyl and amyl, preferably C -C Preferably, R is analiphatic hydrocarbyl radical containing up to 20 carbon atoms and maybe saturated. or unsaturated, straight chain or branched chain.Representative examples of R are methyl, butyl, hexyl, decyl, dodecyl,tridecyl, octadecyl, octadecenyl, octadecadienyl, and3,7-dimethyl-2,6-octadienyl. Also, R may be an hydroxy-alkoxy-alkylradical, such as a 2-hydroxy-3- alkoxypropyl radical.

where R is an aliphatic hydrocarbyl radical as defined for R above, thatis, it may be for example an alkyl, alkenyl, or alkadienyl radicalhaving up to 20 carbon atoms, preferably one having 10 or more carbons.

Also, R may be a hydrocarbon radical containing a carbonyl group, as inwhere R is as defined above. The preferred betaines may be representedgenerically by Formula II which follows:

where x= or 1 andR R R and R are as preferentially defined above. The Rgroups and x may be varied in accordance with the above definition sothat the hydrocarbon content of the dipolar ion is sufiicient forsolubilization of a substantial quantity of the compound in thehydrocarbon to be treated; that is, the compound should contain fromabout 11 to about 35 carbon atoms.

The following are representative betaines of the present invention inwhich R; of Formula I is an aliphatic hydrocarbyl radical attached tonitrogen of a dialkyl glycine radical: N-lauryl betaine (i.e.N-lauryl-N,N-dimethyl glycine), N-hexadecyl betaine, N-octadecylbetaine, N-octaclecenyl betaine, N-lauryl-N,N-dipropyl glycine, C-decylbetaine (i.e., 2-trimethylammonio-dodecanoate), C-dodecyl betaine,C-tetradecyl betaine; and, N-lauryl-C-methyl betaine. The above betainesare described and may be prepared by methods disclosed by Downing andJohnson in U.S. Patent 2,129,264.

Other betaines which may beused according to this invention are those inwhich R, is an aliphatic substituted hydrocarbyl radical, e.g. ROCHCHOHCH of Formula II, attached to nitrogen of an N,N-dialkyl glycine.Representative examples are N-(2-hydroxy-3-butyloxypropyl)betaine,N-(2-hydroxy-3-decy l oxypropyl)betaine,N-(2-hydroxy-3-lauryloxypropyl)betaine, N-[2-hydroxy-3 (3,7 dimethyl 2,6octadienyl)oxypropyl]betaine, N-(2-hydroxy-3-tridecyloxypropyl)betaine,N-(2- hydroxy-3 octadecenyloxypropyl) N,N diethyl glycine and thecorrespondingly substituted -N,N-dipropyl glycine.

The above N-(2-hydroxy-3-alkoxypropyl)-N,N-dialkyl glycines may beprepared by known methods, for example by condensing an'alcohol withepichlorhydrin and reacting the intermediate condensation product thusobtained with an alkali metal salt of an N,N-dialkyl glycine.Preferably, the alcohol will contain from 10 to 20 carbon atoms.Available alcohols of this type are the Lorol fatty alcohol mixtures,e.g. Lorol 5 which contains alcohols having from to 18 carbon atoms withlauryl alcohol predominating; Ocenol fatty alcohols, e.g. Ocenol P whichis principally oleyl alcohol; geraniol (3,7-dimethyl-2,6-octadienol);oxo-alc'ohols, which are mixtures of branched chain primary alkanols,e.g. oxo tridecanol.

As illustrated above, R, R R R and x will be chosensosthat the dipolarion will be soluble in hydrocarbon media to the extent of at least about0.1 lb., preferably at least 0.5 lb., per 1000 barrels (bbls.) of thehydrocarbon. The quantity of the antistatic agent needed to minimize theaccumulation of static electricity in the hydrocarbon substrate willvary with the particular betaine and the particular liquid hydrocarbonproduct, and, will depend, in general, on how prone such hydrocarbon isto accumulate static electricity. Normally, from about 0.5 to 15 lbs. ofadditive, and preferably 1 to 15 per 1000 bbl. of substrate will beemployed. Larger quantities, e.g. 30 lbs/1000 bbl. are operable forantistatic effects, but are usually unnecessary, also such unduly largequantities tend to promote the water emulsification of distillate fuels.While smaller quantites, e.g. 0.1 lb./l000 bbls., may also beoperable,they do not always provide thedesireddegree. of protection.

It should be understood that the presence of the antistatic agent in thehydrocarbon substrate does not do away with the need for adequategrounding of the equipment for containing and handling the hydrocarbonproduct. The antistat apparently functions to minimize the accumulationof static electricity in the hydrocarbonprodnot by conducting the charge(as it tendsto buildup in the hydrocarbon) from the hydrocarbon to thegrounding means.

The use of the betaine antistatic. agents of the present invention isapplicable to any liquid hydrocarbon that boils in the distillate fuelrange and is prone to accumu-v late static electricity in service. Theseinclude hydrocarbon solvents -and distillate fuels, representativeexamples of which are the solvent naphthas, Varsols and Stoddardsolvent, isooctane, both raw and refined kerosines, gasoline (bothautomotive and aviation), jet fuels (JP-4, JP-S and LIP-6), diesel fueland heating oil. The problem appears to be particularly acute with thejet fuels; accordingly, the preferred embodiment of the invention is theuse of the instantly described and claimed antistatic additives in jetfuels.

For convenience in handling, the betaine antistatic agents may be addedto the hydrocarbon substrateas a concentrate in a suitable carrier,which is preferably a liquid hydrocarbon. For example, a 20 to 60%,usually about 50%, by weight of N-lauryl betaine in xylene or keroseneis a preferred form of the antistatic additive.

The antistatic additives may be used in the presence of other additivesthat the hydrocarbon product may normally contain, such as the approvedoxidation and rust inhibitors for the jet fuels.

The betaines of this invention are effective antistatic agents inpractical use concentrations. They are ashless (i.e. being non-metallicthey leave no. harmful residues in the combustion of fuels containingthem) and in general do not promote the tendency of the fuel blendscontaining them to emulsify when mixed with water. This is particularlysurprising and important since betaines in general are regarded assurface active agents and it is known that polar additives that aresurface active, when used in concentrations required for antistaticactivity, have the major disadvantage of failing to meet the watertolerance specifications of fuels such as the jet fuels.

As shown in the examples, jet fuel containing N-lauryl betaine as anantistat not only passes the standard water tolerance test, but shows notendency to accumulate electrostatic charge even after the blended fuelhas been shaken with as much as 5 vol. percentof water. Further, asshown in the examples, N-lauryl betaine, in antistat concentration, isvery elfective to minimize the deterioration of jet fuel when theblended jet fuel is subjected to the thermal stresses of the CFR CokerTest.

The following representative examples illustrate the present invention.

EXAMPLES Testing of the betaine antistatic agents was conducted by theprocedure described by Rogers et al.', Oil and Gas Journal, 55, 166-95(1957.). The equipment employed was essentially a duplicate of thatdescribed in the above reference and was enclosed in a constant humiditychamber.

The tests involve recirculating a sample of the liquid hydrocarbon (withor without additive) at a flow rate of 1450 rah/minute through a columnpacked with Pyrex glass wool (Filtering Fiber Cat. No. 800). The glasswool acts as a charge separator. A tungsten wire electrode inserted intothe packed column leads to an external spark gap, which provides themeans for discharging the accumulating static electricity. The humidityof the atmosphere contained in the Lucite enclosure for the wholeapparatus was maintained at 15% or less, to minimize the eifect ofmoisture on the conductivity of the air through which the spark gapfires. In the present runs the fuel was circulated (and recirculated)through the glass wool packed column for a minute warmup period, andthen a 20 minute run was made during which time the number of dischargeswere counted across the spark gap which had been calibrated to fire at2000 volts (2 kv.). The number of 2 kv. discharges in 20 minutes is ameasure of the tendency of the fuel to accumulate static electricity andthus is a measure of the efiectiveness of the antistatic additive.

In addition, each fuel (with and without additives) was subjected to thewater tolerance test in accord with Method 3251 of Federal SpecificationVVL79lc. The test consists of shaking 80 ml. of the fuel and 20 ml. ofwater (containing a pH 7 phosphate buffer) in a 100 ml. stopperedgraduate cylinder for 2 minutes, and allowing it to stand for 5 minutes.To pass the test, the water and oil phases must break cleanly within the5 minute standing period. Any emulsion or lace in the oil, orpreciiptate at the interface leads to a fail rating.

Example 1 A 50 weight percent xylene solution of N-(Z-hydroxy-3-octadeceny1"oxypropyl) betaine was blended by stirring into a liquidhydrocarbon product as designated below, to provide the concentration ofthe active ingredient also given below. The results obtained in thecirculating static electricity test on the treated and untreatedhydrocarbons follow:

A leaded automotive-type gasoline containing 3 ml. of tetraethyl leadper gallon.

All the above compositions passed the water tolerance test.

The results of the electrostatic test show that the betaine effectivelyminimizes the accumulation of static electricity (being completelyeiiective at the lb./1000 bbl. level) in liquid hydrocarbon products,irrespective of the charge sign the hydrocarbon may acquire.

The N(2-hydroxy-3-octadecenyl-oxypropyl) betaine of this example wasprepared by reacting Ocenol P fatty alcohol with epichlorhyclrin in thepresence of sulfuric acid catalyst, followed by reacting thethus-produced octadecenyl glyceryl ether chloride with sodiumN,N-dimethylglycinate in the presence of KI catalyst.

Employing the correspondingN(2-hydroxy-3-octadecenyloxypropyl)-N,N-diisopropyl glycine, at aconcentration of 15 lbs./ 1000 bbl. in Fuels A and B above, gaveidentical results in the electrostatic and water tolerance tests.

Substantially similar results are obtained on employing other betainesof this type, as indicated in the following example.

Example 2 By the procedure of Example 1, Fuels A and B described abovewere treated to contain N(2-hydroxy-3- octadecyloxypropyl) betaine inthe concentrations given below, and the resulting blends tested to yieldthe following results:

2-kv. Discharges in 20 Minutes Additive Cone, lbs/1,000 bbl.

Fuel A Fuel B None (Control) 720 5. 30 94 7.5 0 31 15 0 0 30. 0 0

All the fuel blends passed the water tolerance test.

Exacple 3 A 50 weight percent solution in xylene of a betaine of theformula:

R 1Ti(c1nn R.-ooiwas blended by stirring into liquid hydrocarbonproducts B and C described in Example 1. R and R of the beta- 1ne, theconcentrations of betaine employed, and the results of the electrostatictest are as described below:

All the hydrocarbon blends passed the water tolerance test.

Example 4 The procedure of Example 3 was repeated, employing:

at a concentration corresponding to 15 lbs/i000 bbl. (This betaine wasprepared by reacting n-dodecyl alphachloroacetate with the sodium saltof N,N-dimethyl glycine.) The results ot the antistatic test inhydrocarbons l3 and D were as follows:

The number of 2-kv. discharges in 20 minutes was reduced from 720 to inpositive'prone Fuel B, and from 459 to 19 in negative-prone Fuel D. Bothcompositions (containing the betaine) passed the water tolerance test.

Example 5 A refined kerosine, with and without Nlauryl betaine at aconcentration corresponding to 1 lb./ 1000 bbl., was vigorously shakenwith 0.1 and 5 volume percent of water for about 5 minutes and themixtures allowed to 7 settle for 16 hours. The electrostatic testresults on the thus-treated products follow:

obtained at room temperature using a platinum ring coated withpolythene.

The results show that fuel containing N-lauryl betaine (1 lb./ 1000bbl.) resists accumulating static electricity even after being contactedwith water.

Example 6 This example shows the beneficial effect of N-lauryl betaineon jet fuel filterability and pre-heater tube deposits as determined inthe CPR Coker Test, in accordance with CRC Manual No. 3, Instructionsfor Operation and Maintenance of CPR Fuel Coker, March 1957, of theCoordinating Research Council, Inc. (The fuel coker is a laboratoryapparatus designed to measure the fuels high temperature stability. Inprinciple, it subjects the test fuel to the same level of temperaturestress and in a manner similar to that occurring in jet engines.)

The results obtained with two LIP-4 jet fuels-one relatively stable(Fuel F) the other relatively unstable (Fuel G)-are tabulated below. Thefollowing code was used to rate each inch of the preheater tubcs 13inches of length:

No visible deposits 1Visible haze or dulling, but no color 2Barelyvisible discoloration 3-Light tan to peacock stain 4-Heavier than 3 CFRFUEL COKER DATA FOR N-LAURYL BETAINE 1 The additive passed the Watertolerance test in both fuels.

9 Total time for the test was 300 minutes; where a pressure drop of 25inches of mercury occurred before 300 minutes had elapsed, the run easstopped to remove the filter and then continued to 300 minutes.

The pressure drop across the filter and the condition of the preheatertube after 300 minutes with respect to tube deposits are a measure ofthe fuels high temperature stabiltiy. The betaine reduced the preheatertube deposits formed with both fuels. It improved the filterability ofthe less stable fuel (G) and did not significantly depreciate thefilterability of the more stable fuel (F).

As stated, none of the betaine additives, in any of the hydrocarboncompositions described above, promoted the emulsification of hydrocarbonwith water, as determined by the water tolerance test.

The non-emulsifying effect of the subject betaines is also shown in thefollowing example.

Example 7 The data below show the eifect of N-lauryl betaine on theinterfaeial tension between jet fuels B and G (JP- and iP-4) and water.The measurements were N-Lauryl Inter-facial Fuel betaine, Tension,

lbs. /l,000 dynes/cm.

bbls.

None 40. 7 7. 5 36. 7 15. 31. 5 None 35. 6 7. 5 31. 6 15. 26. 4

It is currently believed that an additive cannot reduce the interfacialtension between fuel and Water below 15 dynes/em. without interferingwith the operation of fuelwater separators. Thus, the above resultsindicate N- lauryl betaine, at concentrations that are effective forantistatic use, should not cause difiiculty in the separation of fuelfrom water.

It will be apparent that many widely different embodiments of thisinvention may be made without departing from the spirit and scopethereof, and therefore it is not intended to be limited except asindicated in the appended claims.

I claim:

1. A liquid hydrocarbon boiling in the distillate fuel range containingan antistatic quantity, of from 0.1 to 30 pounds per 1000 barrels ofsaid hydrocarbon, of a hydrocarbon-soluble betaine of the formulawherein R is a saturated divalent hydrocarbon radical, R and R aresaturated aliphatic hydrocarbon radicals, and R is an unchargedaliphatic radical taken from the group consisting of hydrocarbonradicals and ether oxygen-, hydroxyl-, and carbonyl-substitutedhydrocarbon radicals, R being free of substituents that promote theemulsification of said liquid hydrocarbon with water, said betainecontaining from about 11 to about 35 carbon atoms.

2. The composition of claim 1 containing an antistatic quantity of from0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquidhydrocarbon.

3. A liquid hydrocarbon boiling in the distillate fuel range containingan antistatic quantity of from 0.1 to 30.0 pounds per 1000 barrels ofsaid liquid hydrocarbon of a hydrocarbon-soluble betaine of the formulawherein x is an integer within the range of 0 to 1, R is an aliphatichydrocarbon radical, R is a saturated divalent hydrocarbon radical, andR and R are saturated aliphatic hydrocarbon radicals, said betainecontaining from about 11 to about 35 carbon atoms.

4. The composition of claim 3 wherein the liquid hydrocarbon containsfrom 0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquidhydrocarbon.

5. A jet fuel liquid hydrocarbon boiling in the distillate fuel rangecontaining from 0.1 to 30.0 lbs. per 1000 barrels of said jet fuel ofN-lauryl-N,N-dimcthyl glycine.

6. The composition of claim 5 containing an antistatic quantity of from0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquidhydrocarbon.

7. As an antistatic additive for liquid hydrocarbons boiling in thedistillate fuel range, (1) a liquid hydro- 10 carbon carrier and (2)from 20-60% by weight of said betaine containing from about 11 to about35 carbon carrier of a hydrocarbon-soluble betaine of the formula atoms.

R2 8. The additive of claim 7 wherein the liquid hydro- R I carboncarrier is xylene.

I 5 9. The additive of claim 7 wherein the liquid hydrocara bon carrieris kerosene. wherein R is a saturated divalent hydrocarbon radical,References Cited in the file of this patent R and R are saturatedaliphatic hydrocarbon radicals, and R is an uncharged aliphatic radicaltaken from the UNITED STATES PATENTS group consisting of hydrocarbonradicals and ether oxy- 10 2,129,264 Downing et a1. Sept. 6, 1938 gen-,hydroxyl-, and carbonyl-substituted hydrocarbon 2,697,656 Stayner et a1.Dec. 2 1, 1954 radicals, R being free of substituents that promote the2,886,423 Vitaiis May 12, 1959 emulsification of said liquid hydrocarbonwith Water, said 2,951,751 McDermott Sept. 6, 1960

1. A LIQUID HYDROCARBON BOILING IN THE DISTILLATE FUEL RANGE CONTAININGAN ANTISTATIC QUANTITY, OF FROM 0.1 TO 30 POUNDS PER 1000 BARRELS OFSAID HYDROCARBON, OF A HYDROCARBON-SOLUBLE BETAINE OF THE FORMULA